I am learning redux using react. I am trying to update an array of numbers based on a button click. I am specifically want to update the counter at specific index based on imported json file.
import React, { Component } from 'react'
import { connect } from 'react-redux'
import { upVote, downVote } from '../store/actions/voteAction';
class Voter extends Component {
render() {
const { count, upVote, downVote, id} = this.props
return (
<div>
<button onClick={() => upVote(id)}>+</button>
The count is {count[id]}
<button onClick={() => downVote(id)}>-</button>
</div>
)
}
}
const mapDispatchToProps = dispatch => ({
upVote: (payload) => dispatch(upVote(payload)),
downVote: (payload) => dispatch(downVote(payload))
});
const mapStateToProps = (state) => ({
count: state.vote.count
})
export default connect(mapStateToProps, mapDispatchToProps)(Voter);
I think my issue comes with how i pass and update the payload in my reducer.
import {UP_VOTE,DOWN_VOTE} from '../actions/actionTypes'
import Mice from './../../imports/mice'
const initialState = {
count: new Array(Mice.length).fill(0)
}
const voteReducer = (state=initialState, action) => {
const id = action.payload
switch(action.type){
case UP_VOTE:
return{
...state, count: state.count[id] + 1
}
case DOWN_VOTE:
return{
...state, count: state.count[id] - 1
}
default:
return state
}
}
export default voteReducer;
I update the array, but every index is still changing and it appears i am still mutating the count array instead of an index inside it.
I have uploaded all my code to CodeSandbox for viewing and experimenting:
CodeSandbox Link
Thanks for reading
Use map method to create a new array, add change one element. The Redux switch will be:
switch (action.type) {
case UP_VOTE:
return {
...state,
count: state.count.map((vote, i) => (i === id ? vote + 1 : vote))
};
case DOWN_VOTE:
return {
...state,
count: state.count.map((vote, i) => (i === id ? vote - 1 : vote))
};
default:
return state;
}
Working code here https://codesandbox.io/s/74pmomo42j
Related
I have a React component that maps state to props to get data via redux. Everything works fine with the action and the value being updated properly in the reducer. My only problem is that when the state value changes, I want my component to re render so that it is always displaying the most up to date value in the reducer. As of right now I have to call a separate function that refreshes the component, but I'd rather have it automatically re render every time that value changes in the reducer.
Action:
export const createPickup = (selected, pickups) => dispatch => {
let icon;
icon = check(selected);
pickups.icon = icon;
return API('/createPickUp/', {
...pickups,
})
.then(res => {
dispatch({type: types.CREATE_PICKUP, res});
})
.catch(err => console.log(err));
};
Reducer:
const initialState = {
pick: [],
};
export default function pickup(state = initialState, action) {
switch (action.type) {
case types.GET_PICK:
return {
pick: action.pickup,
};
case types.CREATE_PICKUP:
return {
pick: [action.res, ...state.pick],
};
case types.DEL_GAME:
return {
pick: state.pick.filter(p => p._id !== action.id),
};
case types.START_GAME:
return {
pick: state.pick.map(p =>
p._id === action.id ? {...p, start: true} : p,
),
};
case types.STOP_GAME:
return {
pick: state.pick.map(p =>
p._id === action.id ? {...p, stop: true} : p,
),
};
default:
return state;
}
}
Use useSelector hook in Functional Component as it automatically subscribes to the state and your component will re-render.
If you are using Class Component then use connect() from redux and mapStateinProps.
I am assuming you have passed the reducer to the global Store.
Now... make sure you have the up to date value in your component.. try consoling it like this...
import {useSelector} from 'react-redux';
const YourCmponent = () => {
const reduxState = useSelector(state => state);
console.log(reduxState);
return <div>Your Content</div>
}
That way you can get access to the redux store. And you don't need to make any other function for updating component You will always get updated value here.
I am learning React Reducer now. I want to build a toggle button that changes a boolean completed value to its opposite each time I click the button.
What I have is an array of states, each state is an object with an id and a completed value set to be true or false. Then I loop through states, setting each state as an Item component and display it on screen.
// App.js file
import React, { useReducer } from "react";
import { AppReducer } from "./AppReducer";
import Item from "./Item";
function App() {
const initialStates = [
{
id: 1,
completed: false,
},
{
id: 2,
completed: false,
},
];
const [states, dispatch] = useReducer(AppReducer, initialStates);
return (
<div>
{states.map((state) => (
<Item item={state} key={state.id} dispatch={dispatch} />
))}
</div>
);
}
export default App;
In the Item component, I display whether this item is completed or not (true or false). I set up a toggle function on the button to change the completed state of the Item.
// Item.js
import React from "react";
const Item = ({ item, dispatch }) => {
function setButtonText(isCompleted) {
return isCompleted ? "True" : "False";
}
let text = setButtonText(item.completed);
function toggle(id){
dispatch({
type: 'toggle',
payload: id
})
text = setButtonText(item.completed);
}
return (
<div>
<button type="button" onClick={() => toggle(item.id)}>Toggle</button>
<span>{text}</span>
</div>
);
};
export default Item;
Here is my reducer function. Basically what I am doing is just loop through the states array and locate the state by id, then set the completed value to its opposite one.
// AppReducer.js
export const AppReducer = (states, action) => {
switch (action.type) {
case "toggle": {
const newStates = states;
for (const state of newStates) {
if (state.id === action.payload) {
const next = !state.completed;
state.completed = next;
break;
}
}
return [...newStates];
}
default:
return states;
}
};
So my problem is that the toggle button only works once. I checked my AppReducer function, it did change completed to its opposite value, however, every time we return [...newStates], it turned back to its previous value. I am not sure why is that. I appreciate it if you can give it a look and help me.
The code is available here.
Here is the working version forked from your codesandbox
https://codesandbox.io/s/toggle-button-forked-jy6jd?file=/src/Item.js
The store value updated successfully. The problem is the way of listening the new item change.
dispatch is a async event, there is no guarantee the updated item will be available right after dispatch()
So the 1st thing to do is to monitor item.completed change:
useEffect(() => {
setText(setButtonText(item.completed));
}, [item.completed]);
The 2nd thing is text = setButtonText(item.completed);, it will not trigger re-render. Therefore, convert the text to state and set it when item.completed to allow latest value to be displayed on screen
const [text, setText] = useState(setButtonText(item.completed));
I have improved your code, just replace your AppReducer code with below.
export const AppReducer = (states, action) => {
switch (action.type) {
case "toggle": {
const updated = states.map((state) =>
action.payload === state.id ? {
...state,
completed: !state.completed
} : { ...state }
);
return [...updated];
}
default:
return states;
}
};
Live demo
Context
The goal is to have a component with a key name being react-rendered in App.js when I press a specific key, registered in another component. The information is being passed thorugh a redux managed state.
The problem
It's simple :
I'm updating my state in my redux reducer but even when duplicating it (I can see it thanks to the redux dev tool that allows me to watch my prevState and my nextState being different)
And the question is as simple :
Why my App.js component won't re-render even after connecting to and
duplicating my state ?
I think I made sure that my state was duplicated with the spreading operation and my redux dev tool display me a good state update without having my prevState and nextState duplicated. I looked through a lot of posts and found only people that forgot to duplicate their state in their reducers, which I did not.
So what's the problem here ??
DevTool Sample
Code
Here is the code, quite simple. The interesting piece is playSound and playedKeys:
App.js :
import React from 'react'
import './App.css';
import { connect } from 'react-redux';
import KeyComponent from './Components/Key'
import SoundPlayer from './Components/Sounds'
const mapStateToProps = (state) => ({
...state.soundReducer
})
class App extends React.Component {
constructor(props) {
super(props);
}
render(){
return (
<div>
{console.log(this.props)}
{
this.props.playedKeys.map(key =>{
<KeyComponent keyCode={key}> </KeyComponent>
})
}
<SoundPlayer></SoundPlayer>
</div>
);
}
}
export default connect(mapStateToProps)(App);
Reducer
export default (state = {allSounds:{},playedKeys:[]}, action) => {
switch (action.type) {
case 'ADD_SOUND':
return reduce_addSound({...state},action)
case 'PLAY_SOUND':
return reduce_playSound({...state,playedKeys : [...state.playedKeys]},action)
default:
return state
}
}
function reduce_addSound (state,action){
let i = 0
state.allSounds[action.payload.key] = { players : new Array(5).fill('').map(()=>(new Audio())) , reader : new FileReader()}
//load audioFile in audio player
state.allSounds[action.payload.key].reader.onload = function(e) {
state.allSounds[action.payload.key].players.forEach(player =>{
player.setAttribute('src', e.target.result);
player.load();
player.id = 'test'+e.target.result+ i++
})
}
state.allSounds[action.payload.key].reader.readAsDataURL(action.payload.input.files[0]);
return state
}
function reduce_playSound(state,action){
state.playedKey = action.payload.key;
if(!state.playedKeys.includes(state.playedKey))
state.playedKeys.push(action.payload.key);
return state
}
Action
export const addSound = (key, input,player) => (dispatch,getState) => {
dispatch({
type: 'ADD_SOUND',
payload: {key : key, input : input}
})
}
export const playSound = (key) => (dispatch,getState) => {
dispatch({
type: 'PLAY_SOUND',
payload: {key : key}
})
}
The component registering the keypresses
import React from 'react'
import { connect } from 'react-redux';
import { playSound } from '../../Actions/soundActions';
const mapStateToProps = (state) => ({
...state.soundReducer
})
const mapDispatchToProps = dispatch => ({
playSound: (keyCode) => dispatch(playSound(keyCode))
})
class SoundPlayer extends React.Component {
constructor(props) {
super(props);
}
componentDidMount () {
this.playSoundComponent = this.playSoundComponent.bind(this)
document.body.addEventListener('keypress', this.playSoundComponent);
}
keyCodePlayingIndex = {};
playSoundComponent(key){
if(this.props.allSounds.hasOwnProperty(key.code)){
if(!this.keyCodePlayingIndex.hasOwnProperty(key.code))
this.keyCodePlayingIndex[key.code] = 0
this.props.allSounds[key.code].players[this.keyCodePlayingIndex[key.code]].play()
this.keyCodePlayingIndex[key.code] = this.keyCodePlayingIndex[key.code] + 1 >= this.props.allSounds[key.code].players.length ? 0 : this.keyCodePlayingIndex[key.code] + 1
console.log(this.keyCodePlayingIndex[key.code])
}
this.props.playSound(key.code);
}
render(){
return <div>
<h1 >Played : {this.props.playedKey}</h1>
{Object.keys(this.keyCodePlayingIndex).map(key =>{
return <p>{key} : {this.keyCodePlayingIndex[key]}</p>
})}
</div>
}
}
export default connect(mapStateToProps, mapDispatchToProps)(SoundPlayer);
Issue
You are mutating your state object.
state.allSounds[action.payload.key] = ...
state.playedKey = action.payload.key;
Solution
Update your reducer functions to return new state objects, remembering to correctly shallow copy each level of depth that is being updated.
export default (state = { allSounds: {}, playedKeys: [] }, action) => {
switch (action.type) {
case 'ADD_SOUND':
return reduce_addSound({ ...state },action);
case 'PLAY_SOUND':
return reduce_playSound({ ...state, playedKeys: [...state.playedKeys] }, action);
default:
return state
}
}
function reduce_addSound (state, action) {
const newState = {
...state, // shallow copy existing state
allSounds: {
...state.allSounds, // shallow copy existing allSounds
[action.payload.key]: {
players: new Array(5).fill('').map(()=>(new Audio())),
reader: new FileReader(),
},
}
};
// load audioFile in audio player
newState.allSounds[action.payload.key].reader.onload = function(e) {
newState.allSounds[action.payload.key].players.forEach((player, i) => {
player.setAttribute('src', e.target.result);
player.load();
player.id = 'test' + e.target.result + i // <-- use index from forEach loop
})
}
newState.allSounds[action.payload.key]
.reader
.readAsDataURL(action.payload.input.files[0]);
return newState;
}
function reduce_playSound (state, action) {
const newState = {
...state,
playedKey: action.payload.key,
};
if(!newState.playedKeys.includes(newState.playedKey))
newState.playedKeys = [...newState.playedKeys, action.payload.key];
return newState
}
Okay I've got it, it's always the simplest stupidest thing that we don't check huh.
Clarification
So my state was properly duplicated with reduce_addSound({ ...state },action) and reduce_playSound({ ...state, playedKeys: [...state.playedKeys] and like I wrote in my question, that wasn't the issue !
Issue
As old as it can get, I wasn't returning a component in my render function.. :
in App.js :
render(){
return (
<div>
{
this.props.soundReducer.playedKeys.map(key =>{
<KeyComponent keyCode={key}> </KeyComponent> //<-- NO return or parenthesis !!
})
}
<SoundPlayer></SoundPlayer>
</div>
);
}
Answer
App.js render function with parenthesis:
render(){
return (
<div>
{
this.props.soundReducer.playedKeys.map(key =>(
<KeyComponent key = {key} keyCode={key}> </KeyComponent> //<-- Here a component is returned..
))
}
<SoundPlayer></SoundPlayer>
</div>
);
}
I'm trying to use Redux to update my Card Component to disable and change colors on click. Redux dispatches the action fine, but it updates all Cards not just the one that was clicked. Each Card has an object associated with it that hold the word and a value. The value is the className I want to use to change the color when clicked
Component
const Card = ({ wordObj, updateClass, isDisabled, cardClass }) => {
const showColor = (e) => {
updateClass(wordObj);
console.log(cardClass)
};
return (
<button
onClick={(e) => showColor()}
disabled={isDisabled}
className={cardClass}>
{wordObj.word}
</button>
);
};
const mapStateToProps = (state) => ({
cardClass: state.game.cardClass,
});
export default connect(mapStateToProps, { updateClass })(Card);
Action
export const updateClass = (obj) => (dispatch) => {
console.log(obj)
dispatch({
type: UPDATE_CARD,
payload: obj,
});
};
Reducer
const initialState = {
words: [],
cardClass: 'card',
isDisabled: false,
};
export default function (state = initialState, action) {
const { type, payload } = action;
switch (type) {
case SET_WORDS: {
return {
...state,
words: payload,
};
}
case UPDATE_CARD:
return {
...state,
isDisabled: true,
cardClass: ['card', payload.value].join(' '),
};
default:
return state;
}
}```
All of your card components are consuming the same cardClass field in the state. When you modify it in this line:
cardClass: ['card', payload.value].join(' ')
All cards that are consuming this field have their classes updated. The same occurs to the isDisable field.
You need to create one object for each card in your state. Here is my implementation (was not tested):
const initialState = {
cards: []
};
export default function (state = initialState, action) {
const { type, payload } = action;
switch (type) {
// create a card object for each word
case SET_WORDS: {
return {
...state,
cards: payload.map(word => {
return { word: word, cardClass: "card", isDisabled: false }
})
};
}
case UPDATE_CARD:
// here i'm using the wordObj.word passed as payload
// to identify the card (i recommend to use an id field)
const cardIndex = state.cards.findIndex(card => card.word === payload.word);
// get the current card
const card = state.cards[cardIndex];
// create an updated card object obeying the immutability principle
const updatedCard = { ...card, isDisabled: true, cardClass: ['card', payload.value].join(' '), }
return {
...state,
cards: [
...state.cards.slice(0, cardIndex), // cards before
updatedCard,
...state.cards.slice(cardIndex + 1) // cards after
]
};
default:
return state;
}
}
Your mapStateToProps selects a string, but said string changes on any updateClass and that causes all your cards to update, because the selection of state.game.cardClass produces a different value, which triggers a new render for the connected component.
Maybe what you want, is something that identifies the selection, i.e. an id for each card, and select with that id in the mapStateToProps to avoid reading the change, because what's happening right now is the following:
Card A[className="card A"] == after dispatch ==> mapStateToProps => [className="card B"]
Card B[className="card A"] => dispatch('B') => mapStateToProps => [className="card B"]
B is updating the state of both A and B, and that's why the extra render occurs
This is from a tutorial assignment from Dave Ceddia's Redux course, I am trying to display the initial state, which contains an array of objects, however it is simply returning undefined and not displaying anything. I am new to React, and I have hit a wall on getting 1) my buttons to display the state, and 2) default state to appear initially.
I have tried to have my component Buttons as a class, and constant.
I have tried stating my initialReducer in the default: return state; in my reducer as well. I have also tried different syntax for my dispatch actions, but nothing seems to be getting to the reducer.
index.js
import React, { Fragment } from "react";
import ReactDOM from "react-dom";
import { getAllItems, addEventToBeginning, addEventToEnd } from "./actions";
import { connect, Provider } from "react-redux";
import { store } from "./reducers";
const Buttons = ({
state,
getAllItems,
addEventToBeginning,
addEventToEnd
}) => (
<React.Fragment>
<ul>{state ? state.actions.map(item => <li>{item}</li>) : []}</ul>
<button onClick={getAllItems}> Display items </button>
<button onClick={addEventToBeginning}> addEventToBeginning </button>
<button onClick={addEventToEnd}> addEventToEnd </button>
</React.Fragment>
);
const mapDispatchToProps = { getAllItems, addEventToBeginning, addEventToEnd };
const mapStateToProps = state => ({
actions: state.actions,
sum: state.sum
});
connect(
mapStateToProps,
mapDispatchToProps
)(Buttons);
reducers.js
const initialState = {
actions: [
{ id: 0, type: "SALE", value: 3.99 },
{ id: 1, type: "REFUND", value: -1.99 },
{ id: 2, type: "SALE", value: 17.49 }
],
sum: 0
};
const newUnit = { id: Math.random * 10, type: "SALE", value: Math.random * 25 };
function eventReducer(state = initialState, action) {
switch (action.type) {
case ADD_EVENT_TO_BEGINNING:
const copy = { ...state };
copy.actions.unshift(newUnit);
return copy;
case ADD_EVENT_TO_END:
const copy2 = { ...state };
copy2.actions.unshift(newUnit);
return copy2;
cut out for cleanliness
case GET_ITEMS:
return {
...state,
actions: state.actions,
sum: state.sum
};
default:
return state;
}
}
export const store = createStore(eventReducer);
example of actions.js (they all follow same format)
export const ADD_EVENT_TO_BEGINNING = "ADD_EVENT_TO_BEGINNING";
export function addEventToBeginning() {
return dispatch => {
dispatch({
type: ADD_EVENT_TO_BEGINNING
});
};
}
UPDATE:
Thank you #ravibagul91 and #Yurui_Zhang, I cut everything but getAllItems out, and changed the state to:
const initialState = {
itemsById: [
{ id: 0, type: "SALE", value: 3.99 },
{ id: 1, type: "REFUND", value: -1.99 },
{ id: 2, type: "SALE", value: 17.49 }
]
};
class Form extends React.Component {
render() {
return (
<div>
{this.props.itemsById
? this.props.itemsById.map(item => (
<li>
{item.id} {item.type} {item.value}
</li>
))
: []}
<button onClick={this.getAllItems}> Display items </button>
</div>
);
}
}
const mapDispatchToProps = { getAllItems };
function mapStateToProps(state) {
return {
itemsById: state.itemsById
};
}
export function getAllItems() {
return dispatch => ({
type: "GET_ITEMS"
});
}
There are multiple problems with your code:
const mapStateToProps = state => ({
actions: state.actions,
sum: state.sum
});
Here you have mapped redux state fields to props actions and sum - your component won't receive a state prop, instead it will receive actions and sum directly.
so your component really should be:
const Button = ({
actions,
sum,
}) => (
<>
<ul>{actions && actions.map(item => <li>{item}</li>)}</ul>
</>
);
your mapDispatchToProps function is not defined correctly. It should be something like this:
// ideally you don't want the function names in your component to be the same as the ones you imported so I'm renaming it here:
import { getAllItems as getAllItemsAction } from "./actions";
// you need to actually `dispatch` the action
const mapDispatchToProps = (dispatch) => ({
getAllItems: () => dispatch(getAllItemsAction()),
});
Your reducer doesn't seem to be defined correctly as well, however you should try to fix the problems I mentioned above first :)
Try not to do too much in one go when you are learning react/redux. I'd recommend reviewing the basics (how the data flow works, how to map state from the redux store to your component, what is an action-creator, etc.).
As you are destructuring the props,
const Buttons = ({
state,
getAllItems,
addEventToBeginning,
addEventToEnd
}) => ( ...
You don't have access to state, instead you need to directly use actions and sum like,
const Buttons = ({
actions, // get the actions directly
sum, // get the sum directly
getAllItems,
addEventToBeginning,
addEventToEnd
}) => (
<React.Fragment>
//You cannot print object directly, need to print some values like item.type / item.value
<ul>{actions && actions.length && actions.map(item => <li>{item.type} {item.value}</li>)}</ul>
<button onClick={getAllItems}> Display items </button>
<button onClick={addEventToBeginning}> addEventToBeginning </button>
<button onClick={addEventToEnd}> addEventToEnd </button>
</React.Fragment>
);
Your mapDispatchToProps should be,
const mapDispatchToProps = dispatch => {
return {
// dispatching actions returned by action creators
getAllItems : () => dispatch(getAllItems()),
addEventToBeginning : () => dispatch(addEventToBeginning()),
addEventToEnd : () => dispatch(addEventToEnd())
}
}
Or you can make use of bindActionCreators,
import { bindActionCreators } from 'redux'
function mapDispatchToProps(dispatch) {
return {
dispatch,
...bindActionCreators({ getAllItems, addEventToBeginning, addEventToEnd }, dispatch)
}
}
In reducer, ADD_EVENT_TO_END should add element to end of the array, but you are adding again at the beginning using unshift. You should use push which will add element at the end of array,
case ADD_EVENT_TO_END:
const copy2 = { ...state };
copy2.actions.push(newUnit); //Add element at the end
return copy2;
Also your GET_ITEMS should be as simple as,
case GET_ITEMS:
return state;